

#include "modbus.h"

unsigned short CRC_16 (unsigned short CRC, unsigned short Cod)
{
	unsigned char i;

	CRC = CRC ^ (0x00FF & Cod);
	for (i = 0; i <= 7; i++)
	{
		if ((CRC & 0x0001) == 0x0001)
		{
			CRC = (CRC >> 1) ^ 0xA001;
		}
		else
		{
			CRC = CRC >> 1;
		}
	}

	return CRC;
}


void reverseWord(sWord * a) {
	unsigned char temp = a->Bytes.ByteHi;
	a->Bytes.ByteHi = a->Bytes.ByteLo;
	a->Bytes.ByteLo = temp;
}


unsigned short calculateMBcrc (mbPacket packet, int type,int lenght)
{
	unsigned short tempCRC;

	int i = 0;

	tempCRC = 0xFFFF;
	
	tempCRC = CRC_16(tempCRC, packet.header.slaveAddress);
	tempCRC = CRC_16(tempCRC, packet.header.op);

	switch(type)
	{
	
	
		case(read_register): 
		{
			tempCRC = CRC_16(tempCRC,packet.tail.readPacketRequest.startWord.Bytes.ByteHi);
			tempCRC = CRC_16(tempCRC,packet.tail.readPacketRequest.startWord.Bytes.ByteLo);
			tempCRC = CRC_16(tempCRC,packet.tail.readPacketRequest.numWord.Bytes.ByteHi);
			tempCRC = CRC_16(tempCRC,packet.tail.readPacketRequest.numWord.Bytes.ByteLo);

			break;
		}

		case(read_register_response):
		{
		
			tempCRC = CRC_16(tempCRC,packet.tail.readPacketResponse.byteNum);

			for(i = 0; i< lenght; i++)
			{
				tempCRC = CRC_16(tempCRC,packet.tail.readPacketResponse.data[i].Bytes.ByteHi);
				tempCRC = CRC_16(tempCRC,packet.tail.readPacketResponse.data[i].Bytes.ByteLo);

			}

			break;	
		}
	}


	sWord CRC;

	CRC.Word = tempCRC;

	reverseWord(&CRC);

	return CRC.Word;
}


unsigned char * serializeMBpacket(mbPacket packet, unsigned char * buffer)
{

	buffer[0] = packet.header.slaveAddress;
	buffer[1] = packet.header.op;
	buffer[2] = packet.tail.readPacketRequest.startWord.Bytes.ByteHi;
	buffer[3] = packet.tail.readPacketRequest.startWord.Bytes.ByteLo;
	buffer[4] = packet.tail.readPacketRequest.numWord.Bytes.ByteHi;
	buffer[5] = packet.tail.readPacketRequest.numWord.Bytes.ByteLo;
	buffer[6] = packet.tail.readPacketRequest.CRC.Bytes.ByteHi;
	buffer[7] = packet.tail.readPacketRequest.CRC.Bytes.ByteLo;

	return buffer;
}

unsigned char * serializeReadResponse(mbPacket packet,unsigned char * buffer,int numWords)
{
	int shift = 3;
	int count = 0;

	buffer[0] = packet.header.slaveAddress;
	buffer[1] = packet.header.op;
	buffer[2] = packet.tail.readPacketResponse.byteNum;

	for(count = 0;count < numWords;count ++)
	{
		buffer[shift+count] = packet.tail.readPacketResponse.data[count].Bytes.ByteHi;
		buffer[shift+1+count] = packet.tail.readPacketResponse.data[count].Bytes.ByteHi;
		shift = shift +1;
	}

	shift = (numWords * 2) +3;

	buffer[shift] = packet.tail.readPacketRequest.CRC.Bytes.ByteHi;
	buffer[shift+1]= packet.tail.readPacketRequest.CRC.Bytes.ByteLo;

	return buffer;
}



mbPacket deserializeMBpacket(unsigned char * buffer)
{
	mbPacket packet;

	packet.header.slaveAddress = buffer[0];
	packet.header.op = buffer[1];

	switch (packet.header.op)
	{

		case read_register:
			packet.tail.readPacketRequest.startWord.Bytes.ByteHi = buffer[2];
			packet.tail.readPacketRequest.startWord.Bytes.ByteLo = buffer[3];
			packet.tail.readPacketRequest.numWord.Bytes.ByteHi = buffer[4];
			packet.tail.readPacketRequest.numWord.Bytes.ByteLo = buffer[5];
			packet.tail.readPacketRequest.CRC.Bytes.ByteHi = buffer[6];
			packet.tail.readPacketRequest.CRC.Bytes.ByteLo = buffer[7];
			break;
		case write_register:
			packet.tail.writeSingleRegRequest.startWord.Bytes.ByteHi = buffer[2];
			packet.tail.writeSingleRegRequest.startWord.Bytes.ByteLo = buffer[3];
			packet.tail.writeSingleRegRequest.data.Bytes.ByteHi = buffer[4];
			packet.tail.writeSingleRegRequest.data.Bytes.ByteLo = buffer[5];
			packet.tail.writeSingleRegRequest.CRC.Bytes.ByteHi = buffer[6];
			packet.tail.writeSingleRegRequest.CRC.Bytes.ByteLo = buffer[7];
			
			break;
	}



	return packet;
}


int validateData(unsigned char * buffer)
{

	return 1;
}


int expectedLenght(mbPacket packet,int type)
{
	
	int lenghtCount = 2; // 2 bytes always for header

	switch(type)
	{
	
		case read_register:
		{
			
			lenghtCount = 6; // 2 bytes header + 2 bytes starting register field + 2 bytes CRC

			lenghtCount = lenghtCount + packet.tail.readPacketRequest.numWord.Word * 2; // expected data number of words by 2 (2 bytes per word)
			break;
		}
	}

	return lenghtCount;
}


static const unsigned char aucCRCHi[] = {
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
	0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 
	0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
	0x00, 0xC1, 0x81, 0x40
};

static const unsigned char aucCRCLo[] = {
	0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03, 0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7,
	0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD, 0x0F, 0xCF, 0xCE, 0x0E,
	0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18, 0x19, 0xD9,
	0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC,
	0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3,
	0x11, 0xD1, 0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32,
	0x36, 0xF6, 0xF7, 0x37, 0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D,
	0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A, 0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 
	0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA, 0xEE, 0x2E, 0x2F, 0xEF,
	0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7, 0xE6, 0x26,
	0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1,
	0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4,
	0x6C, 0xAC, 0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 
	0x69, 0xA9, 0xA8, 0x68, 0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA,
	0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD, 0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5,
	0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73, 0xB1, 0x71, 0x70, 0xB0,
	0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56, 0x57, 0x97,
	0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E,
	0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89,
	0x4B, 0x8B, 0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C,
	0x44, 0x84, 0x85, 0x45, 0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83,
	0x41, 0x81, 0x80, 0x40
};

unsigned short crc16( unsigned char * pucFrame, unsigned short usLen )
{
		
    unsigned char ucCRCHi = 0xFF;
    unsigned char           ucCRCLo = 0xFF;
    int             iIndex;
	
    while( usLen-- )
    {
        iIndex = ucCRCLo ^ *( pucFrame++ );
        ucCRCLo = ( unsigned char )( ucCRCHi ^ aucCRCHi[iIndex] );
        ucCRCHi = aucCRCLo[iIndex];
    }
    return ( unsigned short )( ucCRCHi << 8 | ucCRCLo );
}
